1. Field of the Invention
This invention is directed primarily to the tracking of objects (targets), and more particularly, to an apparatus and method of locking onto and tracking objects. While not limited thereto, the invention is well suited to the tracking of fluid levels (i.e. the top surface of a fluid) within a container, such as a container or tank of fuel.
2. Background Art
Ultrasonic measurement has long been used in the art to track various objects, such as the top surface of a fluid within a tank. Various prior art designs are known in the art, including U.S. Pat. No. 5,511,041; U.S. Pat. No. 5,587,969; U.S. Pat. No. 5,157,639; and U.S. Pat. No. 5,131,271. While the above-identified references address various different issues relative to ultrasonic measurements, they remain problematic for a plurality of reasons. For example, many of the disclosed apparatuses and methods are not particularly well suited to the tracking of rapidly moving targets, such as fluid within a moving container (i.e. fuel in the tank of a moving vehicle). Moreover, others are not particularly well suited to the tracking of fluid levels when the fluid or the area proximate the fluid includes obstructions therein (i.e. material floating on or in the fluid).
Therefore, one object of the present invention is to facilitate the tracking of moving targets, particularly rapidly moving targets.
It is another object of the present invention to facilitate the tracking of moving targets which include obstructions within or near the fluid (i.e. internal tank structures).
These and other objectives will become apparent in light of the present specification, claims, and drawings appended hereto.
The present invention is directed to a method for acquiring the position of at least one object. The method includes the steps of (a) providing a sampling window; (b) obtaining an echo; (c) repeating the foregoing step of obtaining an echo a predetermined number of times; (d) determining which of the at least one echoes received by the receiver comprises a valid echo; and (e) determining if any of the at least one echoes corresponds to a valid target. The step of obtaining an echo comprises the steps of (a) transmitting a pulse at a desired frequency from a transducer; (b) scanning for echoes within the sampling window by a receiver; and (c) receiving at least one echo of the pulse at the receiver which are within the sampling window, the at least one echo having a frequency.
In a preferred embodiment, the step of determining a valid echo comprises the steps of (a) establishing a threshold amplitude; (b) storing portions of each of the at least one received echo which are outside of the threshold amplitude; (c) correlating the frequency of the received at least one echo to the frequency of the respective pulse; and (d) storing the at least one echo if the frequency of the received at least one echo substantially corresponds to the frequency of the respective pulse as a possible target echo.
In one such embodiment, the step of obtaining an echo further comprises the step of dismissing the at least one echo if the frequency of the received at least one echo does not substantially correspond to the frequency of the respective pulse.
In another such embodiment, the method comprises the step of determining the time of occurrence of the at least one echo determined to be a valid echo. In one such embodiment, the step of occurrence determining comprises the step of interpolating one of a first amplitude maxima and minima with a predetermined later amplitude maxima and minima, to, in turn, determine the temporal occurrence of the at least one echo. In another embodiment, the step of interpolating utilizes the greater of the first amplitude maxima and minima with the greater of the fifth amplitude maxima and minima.
In another embodiment, the step of target determining comprises the steps of (a) comparing each of the at least one valid echoes to each other; (b) grouping echoes which are temporally related into an echo group; and (c) identifying each echo group having a predetermined number of temporally related echoes as a target. In one such embodiment, the predetermined number of related echoes comprises at least seventy percent of the predetermined number of pulses.
In yet another preferred embodiment, the step of providing a sampling window comprises the steps of (a) providing a range within which to acquire a target; and (b) dividing the range into a plurality of sampling windows.
In another aspect of the invention, a method of tracking an object is presented. The method includes the steps of (a) acquiring the position of at least one object; (b) selecting the at least one object as a target; (c) determining a sampling window which envelopes the target; (d) transmitting a pulse at a desired frequency from a transducer; (e) obtaining an echo; (f) scanning for echoes within the sampling window by a receiver; (g) receiving at least one echo of the pulse at the receiver which are within the sampling window, the at least one echo having a predetermined frequency; (h) repeating the foregoing step of obtaining an echo a predetermined number of times; (i) determining valid echoes from the target; (j) calculating the current position of the target from the received echoes; and (k) repeating the steps of obtaining, repeating, determining and calculating as desired.
In another preferred embodiment, the method further comprises the step of providing output to an output device corresponding to the current position of the target.
In one embodiment, the step of acquiring comprises the steps of (a) providing a sampling window; (b) obtaining an echo; (c) repeating the foregoing step of obtaining an echo a predetermined number of times; (d) determining which of the at least one echoes received by the receiver comprises a valid echo; and (e) determining if any of the at least one echoes corresponds to a valid target. The step of obtaining an echo comprising the steps of: (a) transmitting a pulse at a desired frequency from a transducer; (b) scanning for echoes within the sampling window by a receiver; and (c) receiving at least one echo of the pulse at the receiver which are within the sampling window, the at least one echo having a frequency that matches the predetermined frequency.
In one embodiment, the method further comprises the step of reacquiring the position of the at least one object if the step of determining a valid target fails to determine a target. In one embodiment, the step of reacquiring comprises the steps of: (a) expanding the previously selected sampling window; and (b) reexecuting the step of repeating with the expanded sampling window.
In another preferred embodiment, the method further comprises the steps of (a) comparing the current position of the target relative to the position of the target during a prior obtained calculation; (b) determining a direction of movement for the target; and (c) expanding the sampling window in the direction of movement. In one such embodiment, the method further comprises the step of contracting the sampling window in the direction opposite of the movement.
In yet another preferred embodiment, the step of selecting comprises the step of automatically selecting the object closest to a predetermined point.
In a preferred embodiment, the step of selecting comprises the steps of (a) outputting parameters corresponding to the various acquired objects to the output device; and (b) inputting the desired object to be tracked by way of the input device.